FA Viewpoints

What are the best number of and locations for LDH intakes? Bill Adams and Rick Riley share their views.
Moving water is a critical function in fire suppression, and large-diameter hoses (LDH) and intakes play a large role in that mission. Fire apparatus needs to be built to accept water from a variety of locations to sustain a sufficient fire flow. This month, we asked Bill Adams and Ricky Riley: What are the best number of and locations for LDH intakes?

Consider LDH Weight and Staffing

It’s improper to answer a question with a question and downright rude to answer it with several. However, sometimes they must be asked to give a rational response. Vendors might tell apparatus purchasing committees (APCs) “what they want to hear” to not lose a sale. Writers are usually careful not to offend readers or advertisers. I’ll pose a few questions, make some general comments, and let readers decide what might be applicable in their individual districts. My commentary is directed at pumpers but can be relevant to any LDH-equipped rig. Common LDH is 4-inch or 5-inch usually coupled in 100-foot lengths. Other seldom-seen sizes include 3½ inch and 6 inch.

APCs often fail to recognize Newton’s third law (from a physics Web site): “For every action, there is an equal and opposite reaction.” In the fire truck world, it means you’ll probably have to move or eliminate something to locate an item in a specific location. When specifying LDH inlets remote from a fire pump, consider the route and space the piping takes, possible friction loss, and cost. Don’t blame the vendor for your idea. Always consider the weight of LDH and the staffing available to move it.


Some departments expect each pumper in their fleet to efficiently move water from a source to the scene in any scenario encountered. Others have job-specific apparatus such as “attack” pumpers that are set up to forward or reverse lay their own supply lines, depending on department protocol. After a set period of time as first out, some attack pumpers are delegated as supply pumpers whose sole function is laying hose. The location and number of LDH inlets purchased today should support a pumper’s role in future years.

Regardless of the modus operandi, apparatus deploy LDH off the back of the rig. Common sense dictates that is where the primary LDH inlet should be. When laying fire to hydrant (aka scene to source), an LDH discharge should also be located at the rear. Rear hookups lessen the possibility of blocking traffic lanes common with side connections. Excess hose can be moved out of traffic lanes before charging. It’s also easier to judge the distance if a short filler length (curb jumper) is required. Nobody wants to say: “Sorry, Chief, the ladder truck couldn’t get by because my supply line blocked the road.” Swiveling suction elbows on side connections might help; a rear suction definitely will. Ditto for a front inlet.

Dual-Function Inlets

LDH inlets are often used to make “big fire” hydrant hookups. It’s conceivable, albeit costly, to have LDH inlets on all four sides, giving the pump operator options when making a plug. (You “make” a plug when you tie into it; you “hit” it when laying away from it.) When reverse laying, pump operators are often by themselves. Make their job easier—especially if you want quick water.

Beware of hose connections on pump panels. National Fire Protection Association (NFPA) 1901,< em> Standard for Automotive Fire Apparatus, prohibits discharges larger than 2½ inch on the operator’s panel. Likewise, it’s dangerous to have pressurized inlets of any size on the operator’s panel adjacent to the operator’s knees or other important body parts.


LDH inlets are often used for drafting. Full-bodied midship pumps are designed to draft from each side. Single-suction front- and rear-mounted pumps work best drafting from where they’re located. Be aware of possible friction losses with LDH suction valves and elbows. Pumps work better when close to the water with straight, unrestricted piping and hose runs to the eye of the impeller.

Front and rear LDH inlets piped to midship-mounted pumps may give a false sense of pump capability. They are ideal for pressurized connections; however, they are often incapable of drafting 100% of the pump’s capacity. Don’t blame the pump manufacturer. Apparatus manufacturers can oversize suction piping, eliminate fittings, and straighten pipe runs to lessen friction loss—if your purchasing specifications require them to do so. NFPA 1901 sentence A.16.6.1 says: “Intakes at the front or rear of the apparatus or otherwise specially situated might not allow drafting rated capacity at rated pressure. The purchaser should specify the flow rates required from auxiliary intakes, especially front and rear intakes or other intakes located 10 ft (3 m) or more away from the pump. If auxiliary intakes are provided, the purchaser should also consider requiring the manufacturer to certify the actual flow rates from auxiliary intakes.”

Don’t specify an unattainable flow rate. Work closely with apparatus and pump manufacturers when writing specifications. Rural departments drafting from portable ponds might not be capable of shuttling the flows capable of large-volume pumps at the scene. Don’t cut yourself short if, a few years after you purchase a new pumper, an improved tanker shuttle can sustain 1,500 gallons per minute (gpm)—and the suction inlet on your rig can’t. When writing purchasing specifications, bear in mind NFPA 1901 does not specify a 1,500-gpm pump has to pump capacity from draft through a single suction hose—unless you specify it has to. Good luck.

BILL ADAMS is a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board, a former fire apparatus salesman, and a past chief of the East Rochester (NY) Fire Department. He has 50 years of experience in the volunteer fire service.

A Number of Considerations for Location

Regardless of how you feel about LDH supply line, its use has certainly increased in the past couple of years, with the 4-inch becoming the preferred line in many departments.

The capability of the LDH certainly enhances the ability to supply large volumes of water to the fireground. These abilities are dependent on the water system in the community if the line is pumped through rather than a direct connection to hydrant. And in the rural water supply application, can the draft site, dry hydrant, or tanker shuttle supply the needed water? After these considerations, then we have to look at receiving and delivering the water through the pump and on the fire scene.

When dealing with the rig, receiving the water can be accomplished in a number of ways. One of the most common ways to receive the LDH line to the intake of the pump is the steamer connections. The appliances and valves that we can attached to the steamer connection can vary, but this method through the steamer is a direct and short route to the heart of the fire pump with no true piping to deal with. A very simple way is the use of a reducer from a standard 6-inch thread from the steamer pipe to a 4-inch stortz coupling on our LDH. This method, while simplistic, does not provide for the operator controlling the water intake after it is hooked up. The flow of water would have to be controlled by the supply engine or shutting or opening the hydrant with a direct connection. Also, by using this method, the fire pump would usually have to be dry instead of wet, which many departments prefer.

The use of a large-diameter valve that can be controlled with a slow closing valve is by far the preferred choice by many departments. This valve attaches directly to the steamer and allows for the operator to control the flow into the pump and can also provide an intake relief device if desired.

Several manufacturers design this type of valve, and they all have certain design characteristics and abilities that can make them optimal for your department, depending on how you operate.

Two of the features that I like to see in this type of valve are a large handle/wheel to allow for the slow closing of the valve, as required by the NFPA, and a storz connection that swivels or easily rotates as the LDH supply line is charged. This will allow for the twists in the hose to make use of the swivel connection to avoid the kinking of the line at the pump if the LDH was not laid flat. These devices also can come with an angled end of the intake to help reduce the amount of space taken up by the LDH in the street and off the pump. If you are dealing with tight streets, this is a very good choice.

Outside of the steamer connection, the receiving of the LDH line can be accomplished from all sides of the rig. These inlets are built and designed when we go to our chosen manufacturer of apparatus and pick and choose where we want them. But there are a number of considerations when making these choices. Starting at the pump, we have to decide how much water we want to flow with the pump. Obviously, that is all based on your department’s geographic response, water distribution, and building stock. Are we looking to add these inlets to give us the ability to receive multiple LDH supply lines and flow large volumes of water? Or are we adding them to provide the pump operator with choices on how to receive the LDH based on apparatus positioning and not blocking streets or driveways with the LDH line?

These inlets should be gated at the pump through a manual slow close valve or an electric valve or air-operated valve. These valves take up space in the pump house, and space can become very cramped very quickly. The piping for these inlets should be as large as the size supply line that you are using to make use of the full amount of water that is being delivered to the pump.

Regardless of where we put these additional inlets around the rig, we have to be mindful of the number of bends and turns we add to the piping. These bends and turns can and will create friction loss and can constrict flow of the volume of water to the pump.

So, when designing these inlets, be sure to review the piping schematics with your manufacturer to make sure there are not excessive bends in the pipes. The LDH inlets that we might place at the rear of the apparatus will always be challenging in respect to where the piping will run and what we have to sacrifice to get the pipe to the rear. This pipe run could increase the height of the hosebed or compartment space on the apparatus. Once again, this is a department’s operational decision for a rig.

The rear inlet can be very beneficial when operators properly position on the fireground to avoid blocking streets and to leave room for the trucks to access the fire building. Placing an LDH inlet on the front of the rig comes with almost the same number of confronts as the rear inlet. The front pipe, depending on your manufacturer, can reduce compartment space, front wheel cramp angle, and piping hanging underneath the front approach angle. By design, I think it is great to have multiple ways to receive the LDH line on all four sides of the apparatus. But consider careful design and operational needs for that rig during the design phase.

The LDH outlets share largely the same amount of design concerns as noted above, but how many and where they are located are an individual department’s decisions.

With that being said, having two of these LDH discharges would allow the apparatus to supply another engine on the fireground and maybe a truck-elevated stream.

So, starting with two might be a good jumping-off point. I would prefer these discharges to be away from the main operator’s pump panel where he controls the fire pump—usually off the passenger side pump panel or off the rear of the apparatus. This number of LDH discharges is based on my desired flow from the fire pump and what we are going to supply on the fireground.

These LDH discharges should also be with full-flow valves and piping to provide the maximum flow. It makes no sense to use LDH hose to receive this large amount of water, then have it constricted through the pump and valves.

RICKY RILEY is the president of Traditions Training, LLC. He previously served as the operations chief for Clearwater (FL) Fire & Rescue and as a firefighter for Fairfax County (VA) Fire & Rescue. He also is a firefighter with the Kentland (MD) Volunteer Fire Department and a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board.

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